More info

Primo suggest the EM258 as a possible replacement for the Panasonic WM-61A. They are different capsules with different specifications as sumarised in the table below, the figures are from the respective manufacturers specifications.Please note the EM258 is not suitable for the "Linkwitz modification".Sensitivity:

EM258 -32±3dB WM61A -34±4dB

S/N Ratio:EM258 74dB WM61A 62dBThe Primo EM258 is identical to the Primo EM158 which is no longer available

Ultrasonic Response

While the EM258 is used mainly for receiving audible signals it is not limited to these frequencies. Like the now discontinued Pansonic WM-61A it has a useful ultrasonic response extending up to 95 kHz. We have done some tests and the EM258 performance exceeds that of the Panasonic WM-61A. Graphs to follow.